The development of environmentally friendly or environmentally benign production processes and technologies posses a key problem today. Therefore, it is of current interest to create methods and devices for obtaining environmentally friendly industrial Aworking fluids and media@ useful to man.
For instance, water and oil-based fluids, called lubricant-coolants, are commonly used in the metal-working industry to cool metals being worked, and fluorine—and cholorine—bearing agents, called freons, are used in the refrigeration industry, to state and conserve products. Both agents are harmful by their impact on man and the environment.
One possible solution for this problem is to use environmentally friendly fluids or media, which are obtained with the aid of vortex tubes using a so called Rank-effect.
Known in the art is a method of controlling thermodynamic processes in a vortex tube using the Rank effect (A. V. Martynov and V. M. Brodyansk AWhat is a Vortex tube, Energy Publishers, 1976, pp. 6-11), according to which a flow of pressurized fluid is fed to a nozzle inlet. In the nozzle inlet the fluid flow is expanded, twisted and delivered to a working tube, wherein the fluid flow is split into cold and hot flows. The cold flow is withdrawn from the first end of the working tube via a cold flow head, and the hot flow is led out of the working tube via a valve placed at the second end of the working tube into a hot flow head. Changing the position of the valve in the beginning of the hot flow head and the nozzle inlet pressure, the parameters of thermodynamic processes in the vortex tube are regulated, which in most cases are the hot and cold flow temperatures, flow rate and the flow efflux speed.
The vortex tube operates as follows: a pressurized medium flow is fed through an admission port into the nozzle inlet. The compressed medium is expanded and split into cold and hot flows, first in the nozzle inlet and then in the working tube. The cold medium flow is carried off through a diaphragm aperture into a cold flow head. Changing the position of the hot flow valve one can vary the rate and temperatures of the cold and hot flows. In order to lower the temperature of the cold flow it is necessary to reduce the cold flow rate by using the valve so as to provide a larger flow section at the hot end of the working tube. Conversely, in order to increase the temperature of the hot flow the valve is used to close down the working tube cross section, thereby reducing the flow section.
Cold and hot flows are formed only if the energy of an incoming flow in the vortex tube is distributed so that certain amount thereof is taken from the cold flow and added to the hot flow. Energy redistribution is, however, a result of a complex thermodynamic processes occurring in the vortex tube. Due to their unique properties, vortex tubes are extensively used in various industries, agriculture and medicine. However, each design of the vortex tube provides for a limited possibility of altering the parameters of cold and hot flows and in order to obtain different parameters of the flows, with traditional implementations one has to modify the design of the vortex tube separately for each and every implementation, which in turn restricts the possibilities of its exploitation.
In EP application 0 684 433 is presented a process, as shown in FIG. 1, for controlling thermodynamic processes in a vortex tube, a vortex tube for carrying out the said process and the use thereof, according to which a process is proposed for controlling thermodynamic processes in a vortex tube by directing a stream of fluid under pressure into a nozzle inlet. In order to obtain the desired characteristics in the cold and hot steams without altering the construction of the tube, the fluid stream in the nozzle inlet is controlled by altering the parameters of state of the thermodynamic processes taking place in the vortex tube. Controlling of the stream in the nozzle inlet is effected by altering the path length of the stream, by splitting the stream into two rotating streams with their own respective path lengths, or by adjusting the speed, flow-rate and pressure of the stream at the entrance to the nozzle inlet. Controlling the stream in the vortex tube is effected by means of the helix mounted in the cavity of the nozzle inlet in such a way that its position in relation to the inlet stream can be altered, and a baffle situated at the entrance to the inlet aperture. The invention can be used for example in machine industry as well as refrigeration and medicine industry etc.
On the other hand as presented in Russian patent number 204 5381, cooling of an apparatus for machining metal can be carried out by a vortex tube, being provided with pneumatic couplings together with cold and hot flow heads and an ionizator with electrodes connected to a power source, whereby the positive electrode is a ring electrode and the negative electrode a needle electrode. Both electrodes are placed in a way that the sharp tips thereof are placed parallel with the cold and hot flow heads. In this case, the cooling unit of the machining apparatus must be provided with an ejector, which is placed by the output end of the cold flow head in a way that the axial placement of the ejector can be adjusted in relation with the output opening of cold flow head and so that it can be connected to a source of desired fluidized medium.
The cooling of a cutting point in the metal machining apparatus operates as follow: air is fed from a source of pressurized air to the nozzle inlet of the vortex tube, in which the air is divided into cold and hot flows. The hot flow gets discharged into the hot flow head through a throttling valve, being placed at the second end of the working tube. The temperature of the cold flow is being regulated in this case traditionally by increasing or decreasing the cross section of the throttling valve. The cold flow is being fed to the cold flow head, having a negative needle electrode therein, in which a high voltage is directed thereto from a current source. The voltage effects a corona arc between the electrodes. In the electric field of the arc occurs ionization of the cold flow, whereby the cold flow is being led as a directed jet to the cutting area of the machining apparatus through an opening in the positive electrode.
On the other hand, a strong jet of ionized air gets inside a cavity inside the ejector causing a vacuum therein. By result thereof, liquid gets collected in the ejector from a liquid source by an elastic piping, the liquid getting sprayed to the ionized cold flow. This high voltage mixture of air and dispersion, comprising ions of oxygen, nitrogen and derivatives thereof, is being fed to the cutting area of the machining apparatus. The mixture cools the point of metal to be cut and moisturizes the graphite dust, being generated during cutting of cast iron, thanks to which dust may not get sprayed in the air of the working environment.
By merely certain structures of a vortex tube, being used particularly for cooling of a cutting area of a machining apparatus, one has, however, limited possibilities to influence on the conditional parameters of the cold and hot flows, whereby in order to achieve adequate alterations of the parameters, it is traditionally necessary to modify the structures of the vortex tube, which for its part limits excessively the possibilities for exploitation of a vortex tube for cooling of a cutting area of a machining apparatus. In addition to the above, humidity of air to be fed inside the vortex tube must be within certain limits (whereby usually drying of the feeding air is required). Limitations for the humidity of the processed air are due to expanding of air in the vortex tube. The reason for this is that in case the air to be fed in the vortex tube is too humid, the operational efficiency of the tube decreases significantly. When excessively humid air is fed to the cold flow head, dying of the corona arc is caused or in other words ionization of the cold flow to be directed to the cutting area of the machining apparatus does not take place. Due to the above, the cooling air flow comprises cutting fluid, but not in ionized state, which is why cooling of the cutting area is not efficient enough and correspondingly oxidated films get generated on the surfaces being processed, in addition to which an excessive amount of heat is spread to the environment.
So, despite the above solutions according to EP 0 684 433 and RU 2045381 and even recent research and development for vortex tubes, there has been found a further need for development of a vortex tube process in order to stabilize the process, without a need for structural modifications of the vortex tube for differing implementations and needs.